Changes the behavior of android fragment transactions to use `add` instead of `replace` on forward navigation.
BREAKING CHANGE:
Changes the internal behavior of Android navigation:
* while navigating forward, the page navigated from is not unloaded anymore
* events order is changed in the sense that now `unloaded` happens after `navigatedFrom` instead of before
There are multiple plus sides to this:
* no more black views on navigation when using opengl (maps, ...)
* navigation is faster, especially the navigation back! No longer need to recreate the page anymore. Navigation forward also gets faster as we no longer unload the previous page
* navigatedFrom event happens faster
* this the default behavior used by most of the android native apps
BREAKING CHANGE:
AndroidTransitionType is now a static member of the Transition class.
BEFORE:
```
import { AndroidTransitionType } from '@nativescript/core/ui/transition';
```
AFTER:
```
import { Transition } from '@nativescript/core';
Transition.AndroidTransitionType.enter; // etc.
```
